Intensive care doctors' preferences for arterial oxygen tension levels in mechanically ventilated patients.

BACKGROUND: Oxygen is liberally administered in intensive care units (ICUs). Nevertheless, ICU doctors' preferences for supplementing oxygen are inadequately described. The aim was to identify ICU doctors' preferences for arterial oxygenation levels in mechanically ventilated adult ICU patients. METHODS: In April to August 2016, an online multiple-choice 17-part-questionnaire was distributed to 1080 ICU doctors in seven Northern European countries. Repeated reminder e-mails were sent. The study ended in October 2016. RESULTS: The response rate was 63%. When evaluating oxygenation 52% of respondents rated arterial oxygen tension (PaO2 ) the most important parameter; 24% a combination of PaO2 and arterial oxygen saturation (SaO2 ); and 23% preferred SaO2 . Increasing, decreasing or not changing a default fraction of inspired oxygen of 0.50 showed preferences for a PaO2 around 8 kPa in patients with chronic obstructive pulmonary disease, a PaO2 around 10 kPa in patients with healthy lungs, acute respiratory distress syndrome or sepsis, and a PaO2 around 12 kPa in patients with cardiac or cerebral ischaemia. Eighty per cent would accept a PaO2 of 8 kPa or lower and 77% would accept a PaO2 of 12 kPa or higher in a clinical trial of oxygenation targets. CONCLUSION: Intensive care unit doctors preferred PaO2 to SaO2 in monitoring oxygen treatment when peripheral oxygen saturation was not included in the question. The identification of PaO2 as the preferred target and the thorough clarification of preferences are important when ascertaining optimal oxygenation targets. In particular when designing future clinical trials of higher vs lower oxygenation targets in ICU patients.

Randomized multicentre feasibility trial of intermediate care versus standard ward care after emergency abdominal surgery (InCare trial).

BACKGROUND: Emergency abdominal surgery carries a considerable risk of death and postoperative complications. Early detection and timely management of complications may reduce mortality. The aim was to evaluate the effect and feasibility of intermediate care compared with standard ward care in patients who had emergency abdominal surgery. METHODS: This was a randomized clinical trial carried out in seven Danish hospitals. Eligible for inclusion were patients with an Acute Physiology And Chronic Health Evaluation (APACHE) II score of at least 10 who were ready to be transferred to the surgical ward within 24 h of emergency abdominal surgery. Participants were randomized to either intermediate care or standard surgical ward care after surgery. The primary outcome was 30-day mortality. RESULTS: In total, 286 patients were included in the modified intention-to-treat analysis. The trial was terminated after the interim analysis owing to slow recruitment and a lower than expected mortality rate. Eleven (7·6 per cent) of 144 patients assigned to intermediate care and 12 (8·5 per cent) of 142 patients assigned to ward care died within 30 days of surgery (odds ratio 0·91, 95 per cent c.i. 0·38 to 2·16; P = 0·828). Thirty (20·8 per cent) of 144 patients assigned to intermediate care and 37 (26·1 per cent) of 142 assigned to ward care died within the total observation period (hazard ratio 0·78, 95 per cent c.i. 0·48 to 1·26; P = 0·310). CONCLUSION: Postoperative intermediate care had no statistically significant effect on 30-day mortality after emergency abdominal surgery, nor any effect on secondary outcomes. The trial was stopped prematurely owing to slow recruitment and a much lower than expected mortality rate among the enrolled patients. REGISTRATION NUMBER: NCT01209663 (http://www.clinicaltrials.gov).

Mortality and postoperative care pathways after emergency gastrointestinal surgery in 2904 patients: a population-based cohort study.

BACKGROUND: Emergency major gastrointestinal (GI) surgery carries a considerable risk of mortality and postoperative complications. Effective management of complications and appropriate organization of postoperative care may improve outcome. The importance of the latter is poorly described in emergency GI surgical patients. We aimed to present mortality data and evaluate the postoperative care pathways used after emergency GI surgery. METHODS: A population-based cohort study with prospectively collected data from six Capital Region hospitals in Denmark. We included 2904 patients undergoing major GI laparotomy or laparoscopy surgery between January 1, 2009, and December 31, 2010. The primary outcome measure was 30 day mortality. RESULTS: A total of 538 patients [18.5%, 95% confidence interval (CI): 17.1-19.9] died within 30 days of surgery. In all, 84.2% of the patients were treated after operation in the standard ward, with a 30 day mortality of 14.3%, and 4.8% were admitted to the intensive care unit (ICU) after a median stay of 2 days (inter-quartile range: 1-6). When compared with 'admission to standard ward', 'admission to standard ward before ICU admission' and 'ICU admission after surgery' were independently associated with 30 day mortality; odds ratio 5.45 (95% CI: 3.48-8.56) and 3.27 (95% CI: 2.45-4.36), respectively. CONCLUSIONS: Mortality in emergency major GI surgical patients remains high. Failure to allocate patients to the appropriate level of care immediately after surgery may contribute to the high postoperative mortality. Future research should focus on improving risk stratification and evaluating the effect of different postoperative care pathways in emergency GI surgery.

Lactate concentrations in the rectal lumen in patients in early septic shock.

BACKGROUND: Previously, we observed that rectal luminal lactate was higher in non-survivors compared with survivors of severe sepsis or septic shock persisting >24 h. The present study was initiated to further investigate this tentative association between rectal luminal lactate and mortality in a larger population of patients in early septic shock. METHODS: A prospective observational multicentre study of 130 patients with septic shock at six general ICU's of university hospitals. Six to 24 h after the onset of septic shock, the concentration of lactate in the rectal lumen was estimated by a 4-h equilibrium dialysis. Dialysate concentrations of lactate were determined using an auto-analyser. RESULTS: The overall 30-day mortality was 32%, with age and Simplified acute physiology scores II and sequential organ failure assessment scores being significantly higher in non-survivors. In contrast, there were no differences in concentrations of lactate in the rectal lumen [2.2 (1.4-4.1) and 2.8 (1.6-5.1) mmol/l (P=0.34)] (medians and 25th-75th percentiles) or arterial blood [2.1 (1.4-4.2) and 2.0 (1.3-3.2) mmol/l (P=0.15)] between non-survivors and survivors. The rectal-arterial difference of the lactate concentration was higher in survivors. There were no differences in blood pressure, noradrenaline dose or central venous oxygen saturation between the groups. CONCLUSION: In this prospective, observational study of unselected patients with early septic shock, there was no difference in the concentration of lactate in the rectal lumen between non-survivors and survivors. TRIAL REGISTRATION: Clinicaltrials.gov (no: NCT00197938).

Terlipressin increased the concentration of L-lactate in the rectal lumen in a patient with septic shock.

Terlipressin--a long-acting analogue of vasopressin--has been described to restore blood pressure in patients with catecholamine-resistant septic shock without obvious complications. We administered low-dose terlipressin (a single i.v.-bolus of 0.5 mg) to a patient with severe, hyperdynamic septic shock requiring high dosage of noradrenalin. After terlipressin the dose of noradrenalin could be reduced by 2/3 to obtain the same blood pressure. Two hours after terlipressin, the cardiac index had decreased from 6.2 to 3.3 l min(-1) m(-2) and the concentration of L-lactate in the rectal lumen, as assessed by equilibrium dialysis, increased from 3.6 to 7.2 mmol l(-1). In contrast, the systemic concentration of L-lactate was unaffected around 2.8 mmol l(-1). After 8 h the effect of terlipressin started to decline, and after an additional 12 h the systemic haemodynamics, dose of noradrenalin and concentrations of rectal and systemic L-lactate were the same as prior to the administration of terlipressin. As a strong vasopressor, terlipressin may have further impaired the metabolic dysfunction in the rectal mucosa either directly via vasoconstriction of mucosal vessels or through decreased cardiac output in this patient with noradrenalin-treated septic shock.

Assessment of the respiratory exchange ratio in mechanically ventilated patients by a standard anaesthetic gas analyser.

BACKGROUND: The respiratory exchange ratio (R) is the CO2 production divided with O2 consumption. R is an essential factor included in several formulas during routine blood gas analysis. Instant and individual measurement of R may be of particular interest to improve the evaluation of each single patient. A standard anaesthetic gas analyser has been recommended for measurement of R among spontaneously breathing healthy subjects, but there is no experience using this method among mechanically ventilated critically ill patients. This study validates the assessment of R by a Brüel & Kjaer gas analyser (B & K) during positive pressure ventilation of intensive care patients. METHODS: The B & K sampled gas from 11 mechanically ventilated patients over a period of 5 min. The recordings of end-tidal values of O2 and CO2 based on fractions (RF) allowed for calculation of RF by the alveolar equation solved for R. The continuous recordings of corresponding values were depicted into an O2-CO2 diagram. A developed computer program calculated estimates of R as the slope of the regression lines related to the full cycle (Rfull) and the expiratory phase only (Rexp). Corrected values of the full respiratory cycle (Rfull*) were also calculated assuming changes of CO2 and O2 volumes during gas exchange. The different estimates of R were compared with simultaneous measurement of a Deltatrac indirect calorimeter (Rdelta). RESULTS: Ten values of RF were within the expected interval of 0.72 < R < 1.00. For the full respiratory cycles, the mean R-value was 0.94 +/- 0.07 and for the expiratory phase the mean R-value was 0.82 +/- 0.08. The O2-CO2 diagram appeared as a convexo-convex loop during each cycle. The agreement of Rexp and Rdelta (Rexp-Rdelta: 0.01 +/- 0.13) were good. CONCLUSION: This study demonstrates that gas measurements by a standard anaesthetic gas monitor can be used for determination of R, and thereby we present an alternative to R calculation made by the Deltatrac monitor.

Evaluation of five oxygen delivery devices in spontaneously breathing subjects by oxygraphy.

Oxygen supply systems may be divided into constant and variable performance systems. As the variable performance systems are widely used, it is relevant to investigate the variation in performance between devices and the influence of oxygen supply on the inspired oxygen fraction. Data were collected from 10 healthy volunteers during the use of one constant performance system and four variable performance systems at different gas flows and inspired oxygen fractions. A thin sampling catheter was placed in the nasopharynx to allow the measurement of the end-tidal oxygen fraction. When oxygen was supplied to variable performance systems, end-tidal oxygen fraction values measured in this way varied less and were more easily quantifiable than inspired oxygen fraction. End-tidal oxygen fraction was used to calculate inspired oxygen fraction. With the variable performance systems, inspired oxygen fraction varied considerably between subjects whereas a constant and equal rise was found for each subject with the fixed performance system. A large nasal catheter was capable of delivering the highest inspired oxygen fraction, whereas the Venturi mask delivered the most precise inspired oxygen fraction. We found oxygraphy useful in the interpretation of measurements made in patients receiving unknown inspired fractions of oxygen.

Preoperative evaluation of intubation conditions in patients scheduled for elective surgery.

Prediction of a difficult airway is a continuing problem. Several tests have been developed in order to overcome this problem. It has been proposed that using more than one test could increase the degree of predictability. One hundred patients scheduled for general surgery were successfully evaluated using three methods: 1. The size of the tongue in relation to the oral cavity (Mallampati gradation). 2. The thyromental and the mandibular length. 3. The atlanto-occipital angle. Seven patients had a difficult laryngoscopy and were difficult to intubate. It was possible to predict differenties in all seven patients, but it was found that only the Mallampati gradation and the atlanto-occipital angle contributed significantly to predictability. The cost of predicting further difficulties in all patients with a difficult laryngoscopy was a false positive prediction in a further 13 patients who had no problems with laryngoscopy or intubation. By increasing the specificity of the tests the number of false positive classifications could be reduced to 10 patients, but this would have led to the missing of one patient with a difficult laryngoscopy.

Erythrocyte 2,3-diphosphoglycerate depletion associated with hypophosphatemia detected by routine arterial blood gas analysis.

OBJECTIVE: To describe a clinical case where an extremely low erythrocyte 2,3-diphosphoglycerate concentration (2,3-DPG) was discovered by routine blood gas analysis supplemented by computer calculation of derived quantities. The finding of a low 2,3-DPG revealed a severe hypophosphatemia. DESIGN: Open uncontrolled study of a patient case. SETTING: Intensive care observation during 41 days. PATIENT: A 44 year old woman with an abdominal abscess. INTERVENTIONS: Surgical drainage, antibiotics and parenteral nutrition. MEASUREMENTS AND RESULTS: daily routine blood gas analyses with computer calculation of the hemoglobin oxygen affinity and estimation of the 2,3-DPG. An abrupt decline of 2,3-DPG was observed late in the course coincident with a pronounced hypophosphatemia. The fall in 2,3-DPG was verified by enzymatic analysis. CONCLUSION: 2,3-DPG may be estimated by computer calculation of routine blood gas data. A low 2,3-DPG which may be associated with hypophosphatemia causes an unfavorable increase in hemoglobin oxygen affinity which reduces the oxygen release to the tissues.

The effect of nasal oxygen flow and catheter position on the accuracy of end-tidal carbon dioxide measurements by a pharyngeal catheter in unintubated, spontaneously breathing subjects.

Reliable recordings of carbon dioxide concentrations during spontaneous respiration can be obtained from a catheter positioned in the hypopharynx. The present study investigated the possible influence on end-tidal carbon dioxide measurement of nasal oxygen administration, position of the sampling catheter and mouth breathing. The study demonstrated that not only can reliable capnographic tracings be obtained from a thin catheter placed in the unintubated airway, but the subject may also receive up to 6 l.min-1 of oxygen via the nasal route without interference with the accuracy of the measurements. Furthermore, the exact position of the sampling catheter tip in the airway is not critical, which means that it may be placed where it causes the patient least discomfort. Finally, mouth breathing caused a mean decrease in end-tidal carbon dioxide of 0.25 kPa compared to nose breathing.

Reliability of CO2 measurements from the airway by a pharyngeal catheter in unintubated, spontaneously breathing subjects.

Although several short communications have appeared describing attempts to record the concentrations of carbon dioxide (cCO2) from the unintubated airway by a catheter placed in the nose, so far only few reports have documented the reliability of the method. To evaluate the reliability of CO2 measurements by a catheter in the open, unintubated airway during spontaneous respiration, a 12 CH PVC catheter was forwarded through the nostril to the hypopharynx and connected to a capnograph in nine healthy volunteers. Another capnograph was connected to a tightly fitting face mask and simultaneous CO2 recordings were attained from the two parts of the airway during normoventilation, hyperventilation and rebreathing. A corresponding blood sample was drawn from the radial artery for blood gas analysis. The configurations of the capnograms recorded from the pharyngeal catheter were similar to those recorded from the face mask. The results were analysed by a multifactor analysis of variance. The carbon dioxide tension (pCO2) was significantly influenced by degree of ventilation (P < 0.0001), subject (P < 0.0001), measurement site (P = 0.030) and interaction subject-ventilation (P = 0.015). In spite of the significant influence of the measurement site, the difference between end tidal carbon dioxide tension (pCO2(ET)) and carbon dioxide tension in arterial blood (pCO2(a)) was small. The mean differences between paired measurements (pCO2(ET)-pCO2(a)) were -0.10 kPa +/- 0.41 kPa (mean +/- SD) for the catheter and -0.20 kPa +/- 0.43 kPa for the face mask. The study demonstrates that reliable recordings of CO2 concentrations during spontaneous respiration can be obtained by a thin catheter positioned in the hypopharynx.

Lactate, pH, and blood gas analysis in critically ill patients.

To obtain information about the relationship between different types of circulatory insufficiency, a series of oxygen parameters and plasma lactate, we have performed a pilot study comprising five patients with circulatory insufficiency. Plasma lactate was measured on a Stat Profile 7 (NOVA Biomedical, USA) and pH/blood gases on an ABL 520 (Radiometer Medical A/S, Denmark). Plasma lactate seems to be inversely related to base excess (BE), whereas no relationship to venous oxygen tension pO2(v) of the vein draining the inadequately perfused region seemed to exist. In one patient we made simultaneous measurements from v. cava inferior., v. cava superior., a. pulmonalis and a. radialis. Simultaneously sampled plasma lactate from different sites differed up to 0.6 mmol/L with the highest value obtained from v. cava inferior. This pilot study indicates that the increase of plasma lactate may vary with the type of circulatory disturbance and the sampling site.

Oxygraphy in spontaneously breathing subjects.

BACKGROUND: Continuous monitoring of O2 and CO2 in the airways of spontaneously breathing patients can be carried out by sampling air to a gas monitor through a catheter placed in the upper airway. The graphical display of O2 (oxygraphy) is a rather new facility. OBJECTIVE: To describe the photo-acoustic and magneto-acoustic technique for CO2 and O2 monitoring in the open unintubated airway, to evaluate the efficacy of oxygen therapy by oxygraphy and to determine alveolar gas tensions and alveolar-arterial partial pressure gradients. DATA SOURCES: O2 and CO2 fractions in the airways were monitored in 9 healthy subjects. Blood samples were drawn from the radial artery. METHODS: The Multigas Monitor 1,304 (Brüel and Kjaer, Naerum, Denmark) was used; end-expiratory measurements were considered as representative for the alveolar gas composition. Arterial blood was analysed by ABL520 (Radiometer Medical A/S, Copenhagen, Denmark). RESULTS: Reliable tracings of gas fractions (FCO2 and FO2) were obtained during the respiratory cycle in all subjects. When oxygen was supplied, FO2 of the airway varied considerably during the inspiratory phase whereas it remained almost constantly during the expiratory phase. The end-expiratory FO2 increased from 0.15 breathing atmospheric air to 0.41 breathing oxygen 15 L/min through a Hudson mask. Alveolar-arterial partial pressure differences were: pO2(A-a): 1.07 +/- 0.85 kPa and pCO2(A-a): -0.04 +/- 0.33 kPa during normoventilation in atmospheric air. CONCLUSION: Continuous monitoring of CO2 and O2 in the airway gives information about the pulmonary gas exchange and the efficacy of oxygen supply. Combined with arterial blood gas analysis the method allows determination of alveolar-arterial CO2 or O2 gradients.